Client-go usage examples

choose_k8s_cluster.go

package main

import (
	"fmt"
	"log"
	"os"

	meta_v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/tools/clientcmd"
)

func main() {
	contextName := ""
	if len(os.Args) >= 2 {
		contextName = os.Args[1]
	}

	client, err := newClient(contextName)
	if err != nil {
		log.Fatal(err)
	}

	pods, err := client.CoreV1().Pods("").List(meta_v1.ListOptions{})
	if err != nil {
		log.Fatal(err)
	}

	for _, pod := range pods.Items {
		fmt.Println(pod.Name)
	}
}

func newClient(contextName string) (kubernetes.Interface, error) {
	configOverrides := &clientcmd.ConfigOverrides{CurrentContext: contextName}

	loadingRules := clientcmd.NewDefaultClientConfigLoadingRules()
	config, err := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(loadingRules, configOverrides).ClientConfig()
	if err != nil {
		return nil, err
	}

	return kubernetes.NewForConfig(config)
}

error_case_test.go

package main

import (
	"errors"
	"fmt"
	"log"

	meta_v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/client-go/kubernetes/fake"
	"k8s.io/client-go/testing"
)

func main() {
	client := newClient()
	setServerError(client)

	pods, err := client.CoreV1().Pods("").List(meta_v1.ListOptions{})
	if err != nil {
		log.Fatal(err)
	}

	for _, pod := range pods.Items {
		fmt.Println(pod.Name)
	}
}

func newClient() *fake.Clientset {
	return fake.NewSimpleClientset()
}

func setServerError(client *fake.Clientset) {
	client.Fake.PrependReactor("list", "pods", func(action testing.Action) (bool, runtime.Object, error) {
		return true, nil, errors.New("server error")
	})
}

get_started.go

package main

import (
	"fmt"
	"log"

	meta_v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/tools/clientcmd"
)

func main() {
	client, err := newClient()
	if err != nil {
		log.Fatal(err)
	}

	pods, err := client.CoreV1().Pods("").List(meta_v1.ListOptions{})
	if err != nil {
		log.Fatal(err)
	}

	for _, pod := range pods.Items {
		fmt.Println(pod.Name)
	}
}

func newClient() (kubernetes.Interface, error) {
	kubeConfig, err := clientcmd.BuildConfigFromFlags("", clientcmd.RecommendedHomeFile)
	if err != nil {
		return nil, err
	}

	return kubernetes.NewForConfig(kubeConfig)
}

in_cluster_client.go

package main

import (
	"fmt"
	"log"

	meta_v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
)

func main() {
	client, err := newClient()
	if err != nil {
		log.Fatal(err)
	}

	pods, err := client.CoreV1().Pods("").List(meta_v1.ListOptions{})
	if err != nil {
		log.Fatal(err)
	}

	for _, pod := range pods.Items {
		fmt.Println(pod.Name)
	}
}

func newClient() (kubernetes.Interface, error) {
	config, err := rest.InClusterConfig()
	if err != nil {
		return nil, err
	}

	return kubernetes.NewForConfig(config)
}

normal_case_test.go

package main

import (
	"fmt"
	"log"

	core_v1 "k8s.io/api/core/v1"
	meta_v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes/fake"
)

func main() {
	client := newClient()
	if err := addTestData(client); err != nil {
		log.Fatal(err)
	}

	pods, err := client.CoreV1().Pods("").List(meta_v1.ListOptions{})
	if err != nil {
		log.Fatal(err)
	}

	for _, pod := range pods.Items {
		fmt.Println(pod.Name)
	}
}

func newClient() *fake.Clientset {
	return fake.NewSimpleClientset()
}

func addTestData(client *fake.Clientset) error {
	pod := &core_v1.Pod{
		ObjectMeta: meta_v1.ObjectMeta{
			Namespace: core_v1.NamespaceDefault,
			Name:      "test",
		},
	}
	_, err := client.CoreV1().Pods(core_v1.NamespaceDefault).Create(pod)
	return err
}